1. Field of the Invention
The present invention relates to a metal core wiring board constituting an electric junction box used to supply electric power to respective electric instruments mounted to a motor vehicle and such. The present invention further relates to an electric junction box having the above-described metal core wiring board.
2. Description of Related Art
In general, a motor vehicle is provided with various electric instruments such as lumps (head lumps, tail lumps), motors for a starter motor and an air conditioner. Therefore, in order to supply electric power to the various electric instruments, a junction block is located at suitable places in the motor vehicle. Such junction block intensively includes a variety of electric circuit units such as fuses and relays.
Since the junction block includes fuses, relays, bus bars and such, it is also called a fuse block or a relay box, or it is generically called an electric junction box. In this specification, the term electric junction box includes the above-mentioned fuse block, relay box and junction block.
The electric junction box includes a case made of an insulating composite resin and arranged to form a frame of the junction box, a printing wiring board received inside the case and provided with the variety of electric components such as above-described relays, connector blocks to which terminals of connectors of a wire harness wired in the motor vehicle are connected. The electric junction box distributes (supplies) electric power supplied by the wire harness from the power source to the respective electric instruments of the motor vehicle.
Recently, more detailed specifications of the motor vehicle are demanded in order to meet a variety of users' demands. Therefore, there is a tendency of the electric instruments of the motor vehicle being more diversified. Densely-mounted electric components and conductor patterns on the printing wiring board causes a generation of heat, and thus there was a problem of a difficulty keeping the temperature of the electric junction box within a specific temperature.
In order to solve the above-described problem, an electric junction box including a metal core wiring board having superior heat-releasing and heat-transferring properties are being proposed. Such electric junction box is disclosed in Japanese Patent Application Publication No. 2006-333583, and the electric junction box according to this prior art includes: a metal core wiring board having various electric components; and connector blocks to which terminals of connectors of a wire harness connected with electric instruments and such are connected.
The metal core wiring board of the above-mentioned prior art includes: a base plate constituted of a conductive metallic core covered by insulators, conductor patterns formed on a surface of the base plate to form a predetermined circuit patterns; and a plurality of through holes penetrating the base plate into which ends of the electric components are to be inserted. The electric components are mounted to the metal core wiring board by inserting the ends of the electric components into the through holes, respectively, and brazing with solder.
The connector block of the above-mentioned prior art includes a tubular housing and a plurality of terminal clamps received inside the housing. The respective terminal clamps are formed into an L-like shape. One ends of the terminal clamps penetrating through the metal core wiring board are brazed to the conductor patterns and the other ends of the terminal clamps are received inside the housing, thereby attaching the connector blocks to the metal core wiring board.
For the electric junction box of the above-described prior art, the metal core wiring board includes thereinside a highly heat-conductive metal core, preventing local elevation of temperature in the metal core wiring board.
However, for the electric junction box of the above-described prior art, the terminal clamps of the connector blocks needed to be attached to the metal core wiring board to connect the metal core wiring board with the external devices (electric instruments). Therefore, a thermal conductivity at connecting portions, at which the terminal clamps and the conductor patterns of the metal core wiring board are connected, is insufficient for smoothly conducting heat generated at the metal core to the terminal clamps. Thus, it is difficult to release the generated heat to an external environment. In addition, the electric junction box of the above-described prior art requires number of components and high manufacturing cost.